Internal combustion engines typically receive fuel that is contained within a fuel tank. An air space or vapor region exists, generally above the surface of the fuel, within the tank. The vapor region is composed of fuel evaporative emissions that can be under pressure. It is desired that the amount of such evaporative emissions contained within the tank be minimized for multiple reasons. One primary reason for such reduction is to minimize emissions of hydrocarbons into the atmosphere, and thus to minimize pollution of the atmosphere.
A fuel tank assembly generally consists of a fuel reservoir, which has a fuel cap and may have a fuel neck therebetween. The fuel neck when incorporated is integrally formed as a single unit with the fuel reservoir. When the level of the fuel in the fuel reservoir is low, the vapor region contains a large amount of fuel vapor under pressure. Consequently, when the fuel cap is detached from the fuel inlet of the fuel reservoir, fuel vapor is forced out of the fuel reservoir into the outside air, causing air pollution. In addition, when fuel is fed into the fuel reservoir from a fuel pump nozzle, the fuel spouted from the nozzle comes into violent contact with and agitates the fuel in the fuel reservoir. This causes bubbles to form in the fuel contained in the fuel reservoir. The collapsing of these bubbles causes further amounts of fuel vapor to be generated in the fuel reservoir, and this fuel vapor flows out from the fuel inlet, causing more air pollution.
Some vehicle fuel systems include valves that are associated with a fuel tank and are configured to vent pressurized or displaced fuel vapor from the vapor region to a separate vapor recovery canister. The canister is designed to capture and store the hydrocarbons entrained in the fuel vapors. Other similar fuel systems include a vapor recovery canister that is attached to a fuel tank. These systems tend to be complex in design, and require an active purging of the vapor recovery canisters. The active purging may be as a result of drawing air through the canister and into an intake manifold as part of an air intake process or through the use of a separate purging circuit.
Another technique that is used to reduce evaporative emission includes a fuel tank cap that is configured with a vapor recovery canister. A purge line extends from the fuel cap to an intake manifold. To purge the canister air is drawn through the canister and into the intake manifold. Not only is this all active system, but it is also is limited in its ability to minimize vapor emissions, due to application feasible size constraints of the fuel cap. Also, the fuel cap can be bulky and difficult or awkward to remove and replace from the fuel tank, as a result of the attached purge line.
One known passive technique of venting or balancing the pressure within a fuel tank consists of a fuel cap that has inlet and outlet vents. Although the fuel cap may be appropriately sized, the fuel cap is incapable of minimizing fuel vapor emissions into the atmosphere.
It is desired to limit daily hydrocarbon evaporative emissions from small off-road displacement engines, such as lawn mowers, all-terrain vehicles, go-karts, trimmers, leaf blowers, generators, power washers, and snow blowers. This may be achieved by capturing and directing emitted hydrocarbons, associated with the fuel tanks of each engine, to combustion chambers for combustion thereof.
Thus, there is a need for an improved technique of controlling the amount of evaporative emissions that escape to the atmosphere that overcomes the above-stated and other disadvantages and limitations associated with prior devices and systems.